If it were implemented correctly I would.
If they added like a $2-5 tax to gun purchases to fund it so it wouldn't cost people directly, made sure that classes were widely available, and limited it to a couple sessions of a reasonable length.

That being said, I very much doubt that there will ever be any actual proposed legislation on the topic that I would agree with. By the time you turn it into a 40 page legal document written by a committee of blowhards and lawyers, even a good idea turns bad.